1. Field
Embodiments of the invention relate to electronic systems, and in particular, to radio frequency (RF) electronics.
2. Description of the Related Technology
Power amplifiers can be included in mobile phones to amplify a RF signal for transmission. For example, in mobile phones having a time division multiple access (TDMA) architecture, such as those found in Global System for Mobile Communications (GSM), code division multiple access (CDMA), and wideband code division multiple access (W-CDMA) systems, a power amplifier can be used to amplify a RF signal for transmission via an antenna. It can be important manage the amplification of a RF signal, as a desired transmitted power level can depend on how far the user is away from a base station and/or the mobile environment. Power amplifiers can also be employed to aid in regulating the power level of the RF signal over time, so as to prevent signal interference from transmission during an assigned receive time slot.
The power efficiency of a power amplifier at a particular input power level can be a function of a variety of factors, including circuit component and layout, power amplifier load, and/or power amplifier supply voltage. To aid in improving the efficiency of a power amplifier, a technique known as envelope tracking can be used, in which the voltage level of the power supply of the power amplifier is changed in relation to the envelope of the RF signal. Thus, when the envelope of the RF signal increases, the voltage supplied to the power amplifier can be increased. Likewise, when the envelope of the RF signal decreases, the voltage supplied to the power amplifier can be decreased to reduce power consumption.